Final answer:
The number with the least value is 0.0004.
Step-by-step explanation:
The number with the least value is 0.0004.
We can compare the numbers by looking at their decimal parts. The decimal part of 0.002 is 2, the decimal part of 0.0019 is 19, and the decimal part of 0.0004 is 4. Since 4 is smaller than 2 and 19, 0.0004 has the least value.